This invention relates generally to magnetic disc drives and head gimbal assemblies. Specifically, this invention relates to magnetic disc drives and head gimbal assemblies having a suspension limiter for preventing large head slaps during severe operational and nonoperational shocks.
Modern computers require media in which digital data can be quickly stored and retrieved. Magnetizable (hard) layers on discs have proven to be a reliable media for fast and accurate data storage and retrieval. Disc drives that read data from and write data to hard discs have thus become popular components of computer systems. To access memory locations on a disc, a read/write head (also referred to as a xe2x80x9csliderxe2x80x9d) is positioned slightly above the surface of the disc while the disc rotates beneath the read/write head at an essentially constant velocity. By moving the read/write head radially over the rotating disc, all memory locations on the disc can be accessed. The read/write head is typically referred to as xe2x80x9cflyingxe2x80x9d head because it includes a slider aerodynamically configured to hover above the surface on an air bearing located between the disc and the slider that forms as the disc rotates at high speeds. The air bearing supports the read/write head above the disc surface at a height referred to as the xe2x80x9cflying height.xe2x80x9d
In conventional disc drives, multiple hard discs are coupled to and rotate about a spindle, each disc presenting two substantially flat surfaces for reading and recording. Typically, multiple rotating hard discs are stacked in a parallel relationship with minimal spacing between them. Accordingly, the read/write heads must be designed to move within the narrow space between adjacent discs and fly close to the disc surfaces. To achieve this positional capability, the read/write heads in typical disc drives are coupled to the distal end of thin, arm-like structures called head gimbal assemblies, which are inserted within the narrow space between adjacent discs. These head gimbal assemblies are made of materials and thicknesses as to be somewhat flexible and allow a measure of vertical positioning as the read/write heads hover over the surface of the rotating discs.
Each head gimbal assembly is coupled at its proximal end to a rigid actuator arm that horizontally positions the head gimbal assembly and read/write head over the disc surface. In conventional disc drives, actuator arms are stacked, forming a multi-arm head stack assembly which moves as a unit under the influence of a voice coil motor to simultaneously position all head gimbal assemblies and corresponding read/write heads over the disc surfaces.
Disc drives have two modes, namely operational and nonoperational. The disc drive is in operational mode when the read/write heads (sliders) are in the data zone and the discs are rotating. Nonoperational mode refers to when the disc drive is not operating (i.e. the discs are not rotating).
There are two main types of disc drives: load/unload and contact start/stop disc drives. Load/unload disc drives xe2x80x9cparkxe2x80x9d their read/write heads when the disc drive system is powered down or when the discs temporarily stop spinning so that the read/write heads rest over ramps which are located off the disc (typically outside the outer diameter of the discs). Contact Start/Stop (CSS) disc drives park the read/write heads in a landing zone located on the disc. This landing zone is typically located on the innermost central region of the discs but not over the data portion of the disc.
In conventional disc drive systems, including both types discussed above, the discs rotate at high velocities and read/write heads are positioned over the discs with very little air gap separation. Contact between the read/write head and the discs, known as a head slap, can be catastrophic. Head slaps occur when the disc drive is shocked (e.g. bumped, jarred or otherwise vibrated) either during operational mode when the discs are rotating or during nonoperational mode when the discs are not rotating. When the disc drive is shocked, the read/write head may lift off the surface of the disc and then return to the surface of the disc making contact with the surface of the disc. Because of this, data can be permanently lost, or the read/write heads and discs can be damaged such that the entire disc drive system no longer functions properly. For load/unload and CSS drives, a head slap can occur during operational mode. For CSS drives, a head slap can also occur during nonoperational mode when the discs are not rotating yet the head is still positioned over the disc surface.
The severity of the head slap will determine the extent of the damage to the disc or head. The shock that causes head slap is characterized by shock pulses that the drive is exposed to, typically half sine shape, with a specific duration (e.g. 0.5 ms to 2.0 ms) and a maximum amplitude in gravitational acceleration or g""s (acceleration due to gravity). At a constant pulse duration, head slaps are typically getting larger with increasing shock amplitude. For a typical 30 series head gimbal assembly, minor head slaps may be occurring around 200 g (0.5 ms) and larger head slaps and multiple slaps at 200-500 g. Note that in the drive, where multiple head gimbal assemblies are mounted on actuator arms and multiple discs are used, head slaps are typically observed at lower g levels. Severe head slaps are of even more concern in low pre-load suspensions because the g""s required to cause a severe head slap are smaller.
One solution that has been found to reduce minor head slaps is to round or radius the corners of the slider instead of using the traditional sharper shaped sliders. This solution has been found to be very effective in reducing and eliminating minor head slaps.
Mechanical latches or stops have been used to reduce non-operational head slap. These stops are not in-situ (part of the head gimbal assembly or head stack assembly) but rather are large mechanical stops attached external to the head gimbal assembly and head stack assembly. These mechanical stops are positioned only to prevent head slap when the head is positioned on its ramp on a load/unload disc drive. In addition to not solving operational head slap, these mechanical stops are large, expensive and unreliable.
Further efforts to reduce media damage caused by head slap have included: decreasing the effective mass of the load beam and slider by decreasing suspension length, width, material thickness, material composition, etc. increasing the pre-load biasing force; and increasing the robustness of the disc surface by using glass substrates, hydrogenated carbon or other tough overcoats, or both. However, under the more stringent requirements of disc drives in more recent times and the desire to build disc drives that can withstand more significant shock, these methods do not prevent head slap from occurring.
In accordance with this invention the above and other problems have been solved by a head gimbal assembly having a base plate; a load beam having a proximal end and a distal end. The proximal end is connected to the base plate. A gimbal assembly supports a transducer and the gimbal assembly is operatively coupled to the distal end of the load beam. A suspension limiter has a proximal end operatively coupled to the actuator arm, and the suspension limiter is in proximity to but not normally in contact with the load beam. The suspension limiter limits movement of the load beam and transducer in shocked conditions when the load beam comes into contact with the suspension limiter.
In accordance with another aspect of the invention, the suspension limiter is operatively coupled to the actuator arm.
In accordance with another aspect of the invention, a magnetic disc drive has a disc, a head stack assembly, and a plurality of head gimbal assemblies. The head gimbal assemblies are operatively coupled to the actuator arm of the head stack assembly. The head gimbal assemblies of the disc drive include suspension limiters which are operatively coupled to the actuator arm.